204
FXUS62 KGSP 132309
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
709 PM EDT Wed Aug 13 2025

.SYNOPSIS...
Abundant moisture over the Southeast will keep scattered to numerous
showers with mainly afternoon thunderstorms through Thursday. As a
somewhat shallow upper ridge builds over our region during the
weekend and early next week, temperatures warm to near normal.
Afternoon thunderstorms become more isolated to scattered from
Sunday into early next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 705 PM EDT Wednesday:

Key Messages:

1) Multiple rounds of showers and storms are expected through
Thursday, producing an isolated flash flood threat.

2) Temperatures a category or so above normal today, and quite
muggy.

Showers and thunderstorms will continue to move across the mountains
and potentially shift east across the foothills of North Carolina
before the loss of daytime heating. Shortwave that will pivot over
the area later this evening is currently located near the AL/GA
line. CAMs have picked up on this and is bringing a slug of
overnight convection across locations along and south of I-85.
Increased PoPs in these locations as a result just based on
consensus and that the environment has been left untapped in this
area. Otherwise, the forecast remains on track.

The western Carolinas remain planted beneath a protrusion of the
subtropical ridge extending from roughly the Florida Peninsula into
the central Appalachians.  The feature of interest is a shortwave
analyzed over southern Mississippi, progged to lift northeast into
the Carolinas this evening and overnight. Mesoanalysis suggests some
3000+ J/kg sbCAPE is present over the low terrain, and this is more
or less supported by what ACARS sounding data is available.

Like yesterday, initiation is the limiting factor and biggest
source of uncertainty in today`s forecast...since for the bulk of
the afternoon, there`ll be no synoptic focus for CI.  Instead, the
HRRR, RRFS, and a few other operational CAMs seem to be keying on
the idea of ridgetop initiation coalescing into a loosely-organized
line/cluster of cells and making a run at the Piedmont.  This is
supported by the convective parameter space; today`s environment
will feature marginally better deep shear than yesterday as flow in
the 850-to-500mb layer becomes constrained, amounting to a solid
15kts and certainly enough for loose organization.  Not enough
for a suitable severe risk, though; the primary hazard for the
next 30 hours remains heavy rainfall and resultant flooding.
The environment is still juiced up with 1.9-2" PWs, and although
storms will move a tad faster today owing to the better flow
aloft, there`s still potential for training/redevelopment over the
mountains where ridgetops will be the primary mode of initiation.

And of course, like yesterday, we can expect multiple rounds.
Once the first, ridgetop-induced round of convection is complete or
waning, the shortwave will slide out of north Georgia and introduce
enough synoptic forcing for scattered showers with embedded thunder
to develop overnight again.  Enough elevated instability will
remain in place for scattered thunder and convectively-enhanced
rain rates.  So, many areas may receive at least two rounds
of potentially heavy rainfall between now and Thursday morning.
Isolated flash flooding appears increasingly likely...so definitely
agree with WPC`s Slight Risk of Excessive Rainfall in the mountains.
Like today, also expect the overnight activity to further moisten
the boundary layer and produce another round of patchy fog and low
stratus Thursday before dawn...or even shortly after daybreak as
occurred today.  Yet another round of afternoon showers and storms
is then expected later in the day.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 100 pm Wednesday: A subtropical anticyclone/upper ridge axis
will dominate the southeast quadrant of the country through the
short term. For our forecast area, this will spell a resumption of
typical mid/late summer weather, with temps expected to be within a
degree or two of normal through much of the period. Convection is
expected each day, with a more typical diurnal cycle...scattered
to numerous coverage of afternoon convection over the mountains
and generally widely scattered activity elsewhere. Stronger
insolation/instability should yield a uptick in the potential for
a few strong/possibly brief severe pulse storms, while locally
excessive rainfall remains possible, especially in locations where
antecedent conditions remain poor due to recent heavy rainfall.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 120 pm Wednesday: The axis of an upper ridge...extending
from an anticyclone retrograding into the Rockies...will remain
over the Southeast through much of the extended. Typical mid/late
summer sensible weather is expected to continue...with forecast
temperatures within a degree or two of normal and daily diurnal
convection. If anything, forecast profiles suggest coverage of
afternoon/evening showers and storms will dwindle a bit early
in week as temps steadily warm aloft. As such, daily PoPs are
generally 30-40% across the mountains, and 10-20% elsewhere Sunday
through Tuesday. The global models are in broad agreement that
heights will begin to fall across the region by the middle of
next week...warranting an uptick in diurnal convective chances
on Wednesday.

&&

.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
At KCLT and elsewhere: VFR conditions will prevail through much
of the evening outside of SHRA/TSRA near KAVL, where associated
restrictions could impact the terminal, so placed a TEMPO for this
potential. Cu field has slowly dissipated, mostly outside the
mountains, but guidance continue to key in on overnight showers and
thunderstorms, especially at the Upstate sites and KCLT. Placed a
prevailing SHRA for the overnight hours and associated restrictions,
but can`t rule out a few lightning strikes as well. Most of the
activity should slip east of the terminals before or around daybreak
Thursday. Still expect some form of IFR to MVFR restrictions with
low stratus and fog possibly developing, but likely to have a later
onset time with the overnight showers and thunderstorms. Expect any
low stratus that develops to scatter by late morning into the early
afternoon hours on Thursday. Otherwise, expect another round of
possible showers and thunderstorms Thursday afternoon and evening,
so placed a PROB30 for TSRA and associated restrictions at all TAF
sites.

Outlook: Showers and thunderstorms with associated restrictions
are expected across the area each day this week. Morning fog/low
stratus is also possible, especially across the mountain valleys.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...DEO
NEAR TERM...CAC/MPR
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...CAC